The present invention relates to tennis balls, and more particularly to tennis balls having a small weight and rebound so that even children of lower age having little experience, adult beginners and adults who lack physical strength and athletic ability, can play tennis without difficulty corresponding to physical strength and skill thereof.
Tennis balls have a standard of ITF (International Tennis Federation), and only those complying with the standard are used in regular games. Usually, general tennis players also use such tennis balls as complying with the above-mentioned standard. Though some tennis balls out of the standard are on the market as practice balls, these balls are not largely out of the standard. That is, there are not much different from the balls complying with the standard and those not complying with the standard in weight, rebound, and the like. The present ITF standards are shown hereinafter for references sake.
______________________________________ Weight 56.7 to 58.5 g Outer diameter 6.35 to 6.67 cm Forward deformation 0.56 to 0.74 cm Return deformation 0.89 to 1.08 cm Rebound 135 to 147 cm ______________________________________
Children of tender age, from 4 to 12 years old, particularly those who play tennis for the first time or have little experience adult beginners and adults who lack physical strength and athletic ability find great difficulty in playing tennis with the above-mentioned balls, since they are too heavy, they bounce too much, they are too hard, they fly too much, particularly their speed becomes too high after bounce for such players. Namely, the tennis balls complying with the standard of ITF made for adults are not suitable for the children of tender age, since they are immature in physical strength, athletic ability and physical constitution. As a result, children are slow in progress for tennis as compared with other sports, and it brings to them a concept that tennis is a dull or uninteresting sport. Then their interesting move from tennis to other sports such as baseball and soccer. Moreover, there is a problem that the children are injured when they continuously play tennis with the above-mentioned balls which overstress their wrists, shoulders and waists and the like. These problems apply the above-mentioned adult beginners and the like.
In order to solve the above-mentioned problems, there is proposed a big ball having about 3 to 11% larger diameter than that of the ITF standard ball which enables players to play leisurely (Japanese Unexamined Patent Publication No. 48385/1986). Players can play tennis leisurely by this type of tennis balls indeed since ball speed becomes slow not only in flight but also after bounce. However, the balls have such disadvantages as they are heavy since the weights are from 54 to 58 g, as the rebound is high since it is about 146 cm, and as the internal pressure of the hollow core is high since it is 0.8 to 1.0 kg/cm.sup.2 higher than the atmospheric pressure. As a result, it is very difficult for children of tender age to play tennis with the big balls as well as ITF standard balls, since children feel they are heavy and they bounce high. Namely, there are no substantial differences between the big balls and ITF standard balls for children of tender age and for adult beginners. The above-mentioned problems are, therefore, not solved by the big balls.
It is an object of the present invention to provide a tennis ball which corresponds to physical constitution, physical strength and athletic ability of players whereby they can play tennis easily, their progress in tennis is accelerated and their amusement in tennis is increased. In the tennis ball of the present invention, the physical properties of the ball such as weight and internal pressure thereof are selected mainly suitable for children of tender age, from about 4 to 12 years old.